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Valid Saturday February 24, 2018 to Wednesday March 07, 2018
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EST February 21 2018Synopsis
: A nearly stationary frontal
boundary is expected to serve as a focal point for hazardous weather across
parts of the East-Central U.S. during the 3-7 day period. Upper-level low
pressure is forecast over the Western U.S. during much of the Hazards period.
The cooler temperatures that are predicted over the western part of the lower
48 states earlier in the period are anticipated to shift eastward later in
Week-2, while some moderation in temperatures is predicted over the West.
Active weather is forecast over much of the extensive southern coast of Alaska
during the Hazards Outlook period. Hazards
Detailed Summary For
Saturday February 24 - Wednesday February 28:
weather across portions of the Middle Mississippi Valley, the Lower Mississippi
Valley, the Southern Plains, and the Tennessee Valley, Sat, Feb 24.
- Heavy rain across portions of the Lower Mississippi Valley to the Ohio
Valley, Sat-Sun, Feb 24-Feb 25.
- Heavy snow from the Central Plains to the Upper Great Lakes, Sat-Sun, Feb
- Flooding possible across portions of the Lower Mississippi Valley, the
Tennessee Valley, the Great Lakes, the Middle Mississippi Valley, the
Northeast, the Upper Mississippi Valley, the Southern Plains, and the Ohio
- Flooding occurring or imminent across portions of the Great Lakes and the
- Flooding likely across portions of the Middle Mississippi Valley, the Great
Lakes, the Ohio Valley, the Upper Mississippi Valley, and the Tennessee Valley.
- Much below normal temperatures across portions of the Northern and Central
Plains, the Rockies, Great Basin, California,the Pacific Northwest, and the
Southwest, Sat-Wed, Feb 24-Feb 28.
- Slight risk of much below normal temperatures from the West Coast, across
the Great Basin, Southwest, and the Rockies to the Northern and Central Plains,
Thu-Mon, Mar 1-Mar 7.
- Moderate risk of much below normal temerpatures from the West Coast, across
the Great Basin, Southwest, and the Northern Rockies to the Northern Plains,
Thu-Mon, Mar 1-Mar 5.
- High risk of much below normal temperatures for portions of the Northern
Plains, the Northern Rockies, and the Northern Great Basin, Thu-Sun, Mar 1-Mar
- Slight risk of heavy precipitation for portions of the Southern Rockies,
the Central Great Basin, California, and the Southwest, Thu-Sat, Mar 1-Mar 3.
- Slight risk of heavy precipitation for portions of the Lower Mississippi
Valley, the Tennessee Valley, mainland Alaska, the Middle Mississippi Valley,
the Southern Appalachians, the Southeast, the Southern Plains, and the Ohio
Valley, Thu-Fri, Mar 1-Mar 2.
- Slight risk of heavy precipitation for portions of the Central Plains, the
Middle Mississippi Valley, the Upper Mississippi Valley, and the Northern
Plains, Fri-Sat, Mar 2-Mar 3.
- Moderate risk of heavy precipitation for portions of mainland Alaska,
Thu-Fri, Mar 1-Mar 2.
- Severe Drought across the Central Plains, the Central Rockies, the Lower
Mississippi Valley, the Central Great Basin, the Northern Plains, the Southern
Rockies, the Middle Mississippi Valley, California, the Southern Plains, and
At the start of the period,
a very slow-moving frontal system is forecast to stretch from Texas
northeastward to the Northeast CONUS. Heavy rain (1.5-2.0 inches or greater in
48 hours) is likely over much of this region. In addition, severe weather is
forecast in the warm sector for parts of the southern Plains, Lower Mississippi
and Tennessee Valleys on Saturday, Feb 24. Vertical wind shear profiles appear
favorable for organized severe storms, though the anticipated severity of this
outbreak may be somewhat offset by weak lapse rates and widespread
The GFS develops the strongest surface low associated with this frontal
boundary this weekend, and produces a swath of heavy snow (6 inches or greater)
to the northwest of the storm track over the Upper Midwest, Feb 24-25. Today's
0z deterministic ECMWF run has come into better agreement with the most recent
(0z and 6z) GFS solutions today, warranting the designation of a
heavy snow hazard from the central Plains northeastward across the Upper
Snow melt and heavy rainfall during the period in areas that have frozen
ground lead to possible, likely, imminent or occurring river flooding across
portions of the southern Plains, Mississippi Valley, the Ohio Valley and Great
Upper-level low pressure and areas of surface high pressure result in
periods of much-below normal temperatures (negative anomalies of 15-25 degrees
F) for much of the Western and North-Central CONUS, Feb 24-28. Upper-level
shortwaves are forecast to cross the northwestern CONUS resulting in periods of
heavy snow (amounts in excess of 6 inches in 24 hours) for parts of
the Cascades, Feb 24-25.
An occluded frontal system is expected to track from the Bering Sea to the
Gulf of Alaska, Feb 24-25. However, predicted wind speeds associated with this
system do not appear to justify a wind hazard on the map. There could be strong
gap winds through the Shelikof Strait (near Kodiak) and lower Cook Inlet, Feb
24-25, but they should be fairly localized in nature. For Thursday March 01 -
Wednesday March 07:
The 8-14 day time period is likely to feature a trough
over the western CONUS, which is likely to shed some energy downstream. A
slight risk over heavy precipitation is indicated for the Southwest, portions
of the Great Basin, and the Sierra Nevadas, for Mar 1-3. Widespread
precipitation amounts are not likely to exceed hazardous thresholds, but in
higher terrain and in west and southward facing slopes, local amounts are
likely to exceed 2 inches of liquid equivalent. Models are progressing some of
that energy to the Lower Mississippi Valley, while other model solutions favor
are more northward excursion. Therefore a slight risk of heavy precipitation
is indicated from eastern Texas to Tennessee and Ohio, as well as over the
Upper Mississippi Valley. The signal is weak, but given the recent flooding in
the Tennessee Valley, and predicted flooding in the 3-7 day period, the
potential for more damaging floods warrants the posting of a hazard.
A mean storm track is forecast to steer storms into western Alaska during
the early portions of Week-2. A moderate risk of heavy precipitation is
indicated as model forecasts depict a slug of moisture moving across western
Alaska on Mar 1-2.
The troughing forecast over the western CONUS supports hazards for much
below normal temperatures. A high risk is delineated from Northern Idaho to
western Nebraska for days 8-11 (Mar 1-4), while moderate (Mar 1-5) and slight
(Mar 1-7) risks are posted from the Great Plains to the West Coast.
The U.S. Drought Monitor, valid on Feb 13, 2018 indicates a slight decrease
in the coverage of severe to exceptional drought (D2-D4) from 18.44% last week
to 18.04% this week. A few of the more substantial revisions made to the map
this week include an increase in D2 coverage across southern California, the
elimination of all D2 areas across the Gulf Coast states from Louisiana to
Florida, and significant 1-category improvements rendered across the Carolinas,
mid-Atlantic, and Northeast.
Forecaster: Anthony Artusa
Click here to see a display of the GFS Ensemble Forecasts
Please consult local NWS Forecast Offices for short range forecasts and region-specific information.